It is known to inflate an inflatable vehicle occupant protection device to help protect a vehicle occupant in the event of a vehicle collision. One particular type of inflatable vehicle occupant protection device is an inflatable tubular structure that inflates from the roof of the vehicle downward inside the passenger compartment between a vehicle occupant and the side structure of the vehicle in the event of a side impact or rollover. A known inflatable tubular structure is inflated from a deflated condition by inflation fluid directed from an inflator to the inflatable tube structure through a fill tube.